A simple correlation for estimation of economic thickness of thermal insulation for process piping and equipment

Where the sole object of applying insulation to a portion of plant is to achieve the minimum total cost during a specific period (evaluation period), the appropriate thickness is usually termed as the economic thickness. The principle is to find at what thickness further expenditure on insulation would not be justified by the additional financial saving on heat to be anticipated during the evaluation period. Although an increase in the amount of insulation applied will raise the initial installed cost, but it will reduce the rate of heat loss through the insulation. Therefore it is necessary to reduce the total cost during the evaluation period. In this work, simple-to-use correlation, employing basic algebraic equations which are simpler than current available models involving a large number of parameters, requiring more complicated and longer computations, is formulated to arrive at the economic thickness of thermal insulation suitable for process piping and equipment. The correlation is as a function of steel pipe diameter and thermal conductivity of insulation for surface temperatures at 100 °C, 300 °C, 500 °C and 700 °C. A simple interpolation formula generalizes this correlation for wide range of surface temperatures. The proposed correlation covers pipeline diameter and surface temperature up to 0.5 m and 700 °C, respectively. The average absolute deviation percent of proposed correlation for estimating the economic thickness of the thermal insulator is 2% demonstrating the excellent performance of proposed simple correlation.